You would have to set a hardware bit to boot from an SSD. You would be limited by USB 2.0 though. Once you set a hardware bit you can’t go back. It should work with 1GB of RAM but the performance would be less than optimal.

Just let me mention that I am using Raspberry 3B as the Unifi Controller 5.8.30 for 7 devices and 36 clients. Works surprisingly well for over a year. That gives justified hope UNMS would be worth trying. Let us know on progress…